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Tube Notching

03-07-2013, 08:57 PM

I have used a few different methods to notch tube over the years. Some that work great and are worth the time to set up others not so much. Today I needed to notch a 40mm diametre tube to fit to a 100mm diametre tube at 90 degrees. I noticed this free download program that has been around a while and thought I would give it a go "Tubemitre". I punched in the data and printed out the result. Used sticky tape to fix the paper template to the tube and with the aid of an air hacksaw cut away the excess in a few minutes. The result without any sanding is just about good enough to start welding.
Pretty cool.

Comment

Works in a pinch but if you do any real work you need to have a means of just setting a degree and go. Pretty cool using the math though. I did my first fish mouths with a similar program close to ten years ago, thought it was the bees knees till I used a hole saw based jig, then even better a nibbler style, and now I use the mill. Just gets more accurate and faster.

Comment

How much did a bit cost that would notch a 100mm or 4" bite out of a 40mm tube?
How long does it take from start to finish?
The tubemitre system with a air hacksaw took about 6 minutes total.
At a cost of $150 because the hacksaw was a Snap On Bluepoint.
The room taken up in my workshop is very little.
As I said this is petty good for what is required to get a really good fit up.

Ji

Grip it and Rip it

Comment

I only have to notch a few pipes every once in a while. I paid $300 for a P & N hole saw set to use for the job on my drill press. Problem with this is that the hole saws don't match tube diameters which means to get a good fit up you have to file or sand. Also the largest hole saw in the set is 75mm or 3" diameter which means more work after the cut is made to make a good fit up for this project. I could use a linisher with tube diameter spindles and a cross slide table to feed the tube into the grinding belt but they cost $2500 and take up half a car space in the workshop. I could pay $25000 and get a CNC mill or $250 000 and get a CNC laser which would take up the size of a car in the workshop. These certainly would speed up the notching but for the few times a year I have to do this the best bang for my buck is this program and an air saw. It will do any diameter tube at any angle with the least waste, takes up no space in my workshop and costs nothing. If you are doing tube work all the time yep this is way to slow, I agree. But then you would have one of those alternatives and a operator that just notches tube, or have the work outsourced by a laser cutting company.

Comment

Okay, I'll buy the reasoning behind that. But I'll caution this. If your using stainless to ward off corrosion, don't use plasma. First of the slag (or whatever you want to call it) is super hard and it is nearly impossible to get rid of and you'll burn up a bigt chunk of change on abrasvies. Second, you'll find that you've most likely desensitized the tubing and it will no long be as corrosion resistant as when you started. The super heating of the tube and resulting oxidation causes the formation of chromium-carbide. This reduces the amount of chromium distributed through the alloy to fight corrosion ( I know that's a simplified version, but it's the basic idea).

I've notched more SS tube than I would ever care to admit. The best way is with an abrasive notcher, or even an endmill notcher (cost prohibitive unless you're doing alot and making money at it). Second best is mill, lathe, or endmill style notcher setup(not as expensive, but still on the pricey end for a hobbiest). After that I'd still have to say hole saw style notcher. If you can setup it up as rigid as possible in a variable speed drill press, your better off, use low low speed and decent pressure and plenty of coolant/lube. If your stuck with a hand drill, get some help to spray on the lube and use as slow a speed you can manage.

As for the air hack saw method mentioned earlier. Works great on that one-off project. Especially with large diameter tubing, when holesaw style notchers won't work. Even better if you only have one or two and can't justify the expense of a notcher. However if it's a big project or you can forsee a few more similar projects in the future, save your pennies and buy a nice notcher, you won't regret it. I made mine, and I can't even begin to tell you the time and money it's save me.

Later,
Kev

Comment

You can cut back on the waste or scrap by not using the drill bit to pilot the hole saw through the tube, if you have a drill press or mill or something like that. I just take the pilot out and clamp the work piece solidly. Line everything up, clamp 'er down and feed the hole saw in, slowly. After all it's really just a saw. Only spinning, not feeding in a line. I don't know what tools you have and I'm not critisizing, just throwing it out there for the masses.

Comment

The largest hole saw I can find at my tool suppliers is 75mm or 3" diameter and I needed 100mm or 4" so a hole saw notcher will not work in my case. SS bluntens bi metal blades very fast and if you had lots of SS tube to cut I would buy a linisher with tube size spindles. The other problem that I have come across is that the hole saws are not very deep so you have to cut from both sides. The alignment then becomes a problem if using a drill press.